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package javax.mail.internet;

import javax.mail.*;
import javax.activation.*;
import java.io.*;
import java.net.UnknownServiceException;
import com.sun.mail.util.PropUtil;
import com.sun.mail.util.FolderClosedIOException;

/**
 * A utility class that implements a DataSource out of
 * a MimePart. This class is primarily meant for service providers.
 * 
 * @see javax.mail.internet.MimePart
 * @see javax.activation.DataSource
 * @author John Mani
 */

public class MimePartDataSource implements DataSource, MessageAware {
	/**
	 * The MimePart that provides the data for this DataSource.
	 * 
	 * @since JavaMail 1.4
	 */
	protected MimePart part;

	private MessageContext context;

	/**
	 * Constructor, that constructs a DataSource from a MimePart.
	 */
	public MimePartDataSource(MimePart part) {
		this.part = part;
	}

	/**
	 * Returns an input stream from this MimePart.
	 * <p>
	 * 
	 * This method applies the appropriate transfer-decoding, based on the
	 * Content-Transfer-Encoding attribute of this MimePart. Thus the returned
	 * input stream is a decoded stream of bytes.
	 * <p>
	 * 
	 * This implementation obtains the raw content from the Part using the
	 * <code>getContentStream()</code> method and decodes it using the
	 * <code>MimeUtility.decode()</code> method.
	 * 
	 * @see javax.mail.internet.MimeMessage#getContentStream
	 * @see javax.mail.internet.MimeBodyPart#getContentStream
	 * @see javax.mail.internet.MimeUtility#decode
	 * @return decoded input stream
	 */
	public InputStream getInputStream() throws IOException {
		InputStream is;

		try {
			if (part instanceof MimeBodyPart)
				is = ((MimeBodyPart) part).getContentStream();
			else if (part instanceof MimeMessage)
				is = ((MimeMessage) part).getContentStream();
			else
				throw new MessagingException("Unknown part");

			String encoding = MimeBodyPart.restrictEncoding(part, part.getEncoding());
			if (encoding != null)
				return MimeUtility.decode(is, encoding);
			else
				return is;
		} catch (FolderClosedException fex) {
			throw new FolderClosedIOException(fex.getFolder(), fex.getMessage());
		} catch (MessagingException mex) {
			throw new IOException(mex.getMessage());
		}
	}

	/**
	 * DataSource method to return an output stream.
	 * <p>
	 * 
	 * This implementation throws the UnknownServiceException.
	 */
	public OutputStream getOutputStream() throws IOException {
		throw new UnknownServiceException("Writing not supported");
	}

	/**
	 * Returns the content-type of this DataSource.
	 * <p>
	 * 
	 * This implementation just invokes the <code>getContentType</code> method
	 * on the MimePart.
	 */
	public String getContentType() {
		try {
			return part.getContentType();
		} catch (MessagingException mex) {
			// would like to be able to reflect the exception to the
			// application, but since we can't do that we return a
			// generic "unknown" value here and hope for another
			// exception later.
			return "application/octet-stream";
		}
	}

	/**
	 * DataSource method to return a name.
	 * <p>
	 * 
	 * This implementation just returns an empty string.
	 */
	public String getName() {
		try {
			if (part instanceof MimeBodyPart)
				return ((MimeBodyPart) part).getFileName();
		} catch (MessagingException mex) {
			// ignore it
		}
		return "";
	}

	/**
	 * Return the <code>MessageContext</code> for the current part.
	 * 
	 * @since JavaMail 1.1
	 */
	public synchronized MessageContext getMessageContext() {
		if (context == null)
			context = new MessageContext(part);
		return context;
	}
}
